Axial flow throttling valve

ABSTRACT

This application discloses a tube-type throttling valve assembly and the particular construction of the valve, along with the control passages and associated pilot controls.

This is a continuation of application Ser. No. 697,492, filed June 18,1976 now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to a flexible tube-type throttling valve assemblyparticularly useful in gas pressure control.

In a preferred configuration, an expansible tube is carried on a coresleeve which is shaped for easy and economical construction andassembly. The sleeve has axially spaced inlet and outlet openings withan intermediate barrier preventing axial flow through the sleeve. Thissub-assembly is inserted into the body of the valve and seated on bossesprovided in the valve and the cover member. A chamber for control fluidis provided in the body around the flexible tube, and fluid passagewaymeans is provided from upstream of the valve to transmit the upstreamfluid to the chamber. In this passageway is an automatically varyingflow restrictor for controlling the rate of admission of fluid to thechamber. In addition, a passageway to the downstream side of the valve,controlled by pilot means, regulates the rate of outflow of fluid fromthe chamber.

OBJECTS OF THE INVENTION

It is an object of this invention to provide a flexible tube-type valvewhich maintains a more uniform pressure level over a wider range of flowrates than previous devices.

It is a further object of this invention to provide a variablerestrictor in the upstream line to the control chamber to enhance theeffect of the pilot means for regulating the outflow of fluid from thechamber.

It is a further important object of this invention to provide a compactunitary control assembly which is easy to assemble and maintain, andwhich is useful in a variety of services, by merely using the pilot forthe desired range.

BRIEF SUMMARY OF THE INVENTION

In accordance with this invention, the assembly comprises a flexible,expansible tube stretched over a core sleeve having upstream anddownstream flow openings and an intermediate barrier blocking axialflow. A series of openings around the core are arranged to beselectively covered and uncovered by the flexible tube in response todifferential pressures on the tube. For this purpose a chamber aroundthe tube is connected to the upstream and downstream flow passages. Inthe downstream passage is a pilot valve for controlling withdrawal offluid from the chamber, while in the upstream passage is mounted anautomatically varying restrictor for simultaneously automaticallycontrolling entry of pressure fluid to the chamber. All the controlfluid passages, the pilot valve, and the automatic restrictor areinstalled in the valve housing, making an efficient and compactinstallation. Provision is made for mounting a variety of pilot controlelements, to allow a wide range of services from this configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of one embodiment of anexpansible tube throttling valve assembly;

FIG. 2 is a similar sectional view of the control passages and theautomatic restrictor on a larger scale, and

FIG. 3 is a graph of pressure vs. flow showing the improved performanceattained by the automatic restrictor.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The assembly as shown in FIG. 1 includes a valve 10 having a housing 11and a control element 70. Housing 11 includes a body 20 and a covermember 28 over one end of the body. Inside body 20, in the flow passage,is a slotted cage 22 with a barrier 24, and a resilient expansiblesleeve 26 held in place by a cover member 28. The assembly has an inletpassage 12 and outlet passage 14. This assembly is adapted to be mountedin a fluid-line 16a-16b and to be held in place by the flanges of thepipeline. These flanges are drawn together to hold the valve betweenthem by bolts one of which is shown at 18.

As depicted in FIG. 1, the expansible sleeve 26 is shaped with inturnedflange members 32 on either end. Sleeve 26 is pulled over cage 22, theninserted into body 20 until the flange and corresponding end of cage 22abut shoulder 34 on outlet 14. Cover member 28, with inlet passage 12,is made to interfit with body 20, and has a shoulder 36 adapted toengage the other end of cage 22 and the other inturned flange 32 of thesleeve 26. Suitable seal means 38 is located between cover 28 and body20.

A chamber 30 surrounds sleeve 26. Referring to FIGS. 1 and 2, it can beseen that the top 40 of valve body 20 is enlarged to accommodate portingand manifold 42, which is open to chamber 30. The ports 44 and 46connect manifold 42 to the upstream pressure and the downstream side ofvalve 10, respectively.

With reference to FIG. 2, we see the inlet line consists of bore 48 incover 28, connected to port 44. The bore 48 has a step or shoulder 50and an enlarged portion 52 in which is mounted a floating plug 54. Plug54 has a tapered nose portion 56 which cooperates with shoulder 50 togovern the inflow of fluid to port 44. Plug 54 also has a shoulder 58against which a spring 60 bears. The other end of spring 60 is seated onshoulder 50 to bias plug 54 towards the open position. A longitudinalbore 62 through plug 54 allows the upstream pressure to act against theend 64 of the plug. O-ring 66 seals the bore 52, and threaded cap 68closes the end of the bore and provides a limit stop for plug 54.

From the foregoing, it will be seen that the upstream pressure istransmitted through bore 48 and port 44 to manifold 42 (and chamber 30),subject to restriction by floating plug 54.

Referring to FIGS. 1 and 2, on the outlet side of manifold 42, port 46connects to a pilot regulator 70. In the illustrated embodiment,regulator 70 has a spring-biased diaphragm 72, which is acted upon bydownstream pressure through port 74. Variations in this downstreampressure, which is conducted to port 74 by piping which is not shown,modify the position of the diaphragm, which is connected to a pilotvalve 76 seated in a recess 78 in the top 40 of the valve body 20 by avalve stem 80, in a well-known construction for pilot regulators. Theconstruction of the pilot regulator, except as herein described is toowell-known to require further amplification. Depending on the range ofservice desired, any of a number of pilot regulators can be used in themanner described herein.

The seat assembly 82 of valve 76 is threaded into the small portion of astepped bore 84 in the bottom of regulator 70. The bottom face 86 of theregulator seats upon the top 40 of valve body 20, and is sealed, as byO-ring seal 88.

In this embodiment, seat assembly 82 projects from the bottom ofregulator 70 into recess 78 in the top of main valve body 20.

Another seal 90 seals the interface between recess 78 and seat assembly82 in the top 40 of the main valve body.

Referring now to FIG. 2, counterbore 92 of stepped bore 84 is connectedto manifold 42 by outlet port 46. Around seat assembly stem 94 radialholes 96 connect this counterbore area 92 with axial passage 98 in theseat stem 94. Valve stem 80, connected with diaphragm 72, projectsthrough passage 98, with an O-ring seal 100 sealing the upper portion ofthe stem 80 in passage 98. Stem 80 has a reduced diameter portion 102,providing considerable clearance for flow of fluid in passage 98. On thebottom is sealing member 104 of stem 80 to engage the bottom of seatstem 94, to block flow of fluid from passage 98 when the pilot regulator70 is in one limit position. This sealing member is retained on stem 80by a nut 106 threaded on threaded portion 108 of stem 80.

The recess 78 in the body is sufficiently deep to allow movement of stem80 in response to movement of diaphragm 72. In the wall of recess 78below valve 76 is an outlet port 110 which connects the recess withoutlet passage 14 downstream of cage 22. From the foregoing, it will beseen that the pressure in manifold 42 and chamber 30 is controlled inpart by the pilot 70, which is itself governed by the pressuredownstream of the valve 10. Modifying the manifold pressure is thefloating plug, or variable restrictor 54.

It is obvious that any of a number of pilot controls is useful with thisassembly, and the manifold ports can be adjusted to suit therequirements of the different pilots. For example, the outlet port 46from manifold 42 could enter recess 78 at the bottom, and outlet port110 to the downstream passage 14 could connect with counterbore 92.

Turning now to FIG. 3, we see a comparison of the performances of agiven throttling valve assembly. The differences in performance werecaused by changes in the inlet flow to the manifold. In the one case, anopen line connecting the inlet 12 of the valve with manifold 42 wasused. Placing a fixed restrictor in the line, as is commonly done atpresent, increased the range of flow rates over which the assembly wasoperable, but the pressure drop for each increment in flow rates wasstill large. With the variable restrictor in the inlet line to controlinlet flow to the manifold, the pressure remained nearly constant overessentially the entire range of flow rates. Thus, it can be seen thatfluctuating demand rates downstream, varying the rate of flow throughthis assembly, has a minimal effect on downstream line pressure,providing improved performance in operation.

In operation, as demand changes downstream, the pilot regulator 70changes the setting of valve 76, changing the pressure in manifold 42and control chamber 30. Flow into chamber 30 is modified by variablerestrictor 54, and provides the operating characteristics shown on FIG.3 as the curve labeled "with variable restrictor" As an example, if flowthrough valve 10 is low or minimal, the variable restrictor is open itswidest, under the influence of spring 60 and the differential pressure.If added load downstream decreases the downstream pressure, thediaphragm of pilot regulator 70 moves downwardly, as seen in FIGS. 1 and2, opening pilot valve 76. This produces a drop in pressure in manifold42, and a corresponding pressure drop on shoulder 58 of plug 54.Upstream pressure, applied through bore 62 to the top 64, moves floatingplug 54 downwardly into bore 48 restricting the flow around the pluginto the inlet port 44 and manifold 42. This allows resilient sleeves 26to open further, due to the increased pressure differential betweeninlet 12 and control chamber 30. On the opening of boot 26, increasedflow takes place, which restores the pressure downstream, which in turnmoves pilot regulator 70 to a more restrictive opening of its valve 76.This in turn restricts the flow through port 46 which, in its turn,increases the pressure in manifold 42 and control chamber 30. Theincreased pressure in the manifold is also transmitted to shoulder 58 offloating plug 54, floating plug 54 adjusts to the pressure increaseinfluenced by shoulder 58 and spring 60.

As can be seen from the above description of the operation of thefloating plug in the automatic restrictor, it acts to modify theoperation of the system. Obviously, if the load downstream decreases,the reverse operation of the system takes place. The modifying effect isshown in FIG. 3, giving a very small change in pressure for relativelylarge changes in flow rates as compared to previous methods ofmodification of the inlet line.

We claim:
 1. A self-contained valve assembly for controlling the flow of gaseous fluid in a pipeline to maintain uniform downstream pressure with varying downstream load, comprising a housing having a main fluid passage therethrough, cage means and a resilient boot member in said main passage for controlling the flow of fluid therethrough, a chamber formed in the housing around at least a portion of said boot means, upstream passage means wholly contained in said housing connecting said chamber with said main passage at a point upstream of said cage, a variable restriction in said upstream passage means to control the rate of entry of upstream control fluid into said chamber, downstream passage means wholly contained in said housing connecting said chamber with said fluid passage at a point downstream of said cage, diaphragm controlled pilot valve means mounted on said housing having a control valve projecting into said downstream passage means to control the flow of control fluid out of said chamber through said downstream passage means, and means on said pilot valve means to facilitate a fluid connection between the diaphragm of said valve means and said pipeline downstream of said valve.
 2. The invention defined in claim 1 in which said restriction comprises a seat in said upstream passage means, a pressure controlled plug in said passage means adapted to cooperate with said seat to provide a variable restriction in said passageway, biasing means to bias said plug away from said seat, and means to apply upstream control pressure to said plug in opposition to the force of said biasing means.
 3. The invention defined in claim 2 in which said last mentioned means is a passage in said plug through which the upstream control pressure is applied to the end of said plug which is remote from said seat. 